Unburned Hydrocarbon Emissions Research Articles

Modeling Civil Aviation Emissions with Actual Flight Trajectories and Enhanced Aircraft Performance Model

Aviation emissions are continuously increasing along with the rapid development of air transportation, and results in the deterioration in regional air quality and the global climate. Accurate emission estimation is of great importance for relevant policies promotion and the sustainable development of the environment. Previous studies focused on the total emissions of a flight and lacked high precision in both spatial and temporal resolutions, especially aviation activities near ground. In this research, we propose an open-sourced emission calculation framework based on actual flight trajectories (TrajEmission), which calculates both the ground and airborne emissions simultaneously according to the configuration parameters, trajectory characteristics, and ambient conditions. We compare the emission results with five emission inventory methods. The results indicate that pollutant (nitrogen oxides, carbon monoxide, and unburned hydrocarbons) emissions in the landing and takeoff (LTO) cycle might usually be underestimated due to a lack of trajectory-based methods. In addition, in the overall results, the method based on the great circle route leads to an overestimation of 56.8% of pollutant emissions compared to the method based on actual routes. We also investigate the extent to which other factors could influence the emission results. To summarize, the TrajEmission framework can build inventories for the whole process of flight movements with high spatial–temporal resolutions and provide solid data support for environmental science and other related fields.

Experimentally Investigating the Potential of Iso-Stoichiometric GEM Blends as a Drop-in Replacement for E50 in SI Engines

Background: Research on alternative fuels for internal combustion engines is crucial due to climate change and energy security concerns. Ethanol-blended gasoline has been a popular alternative fuel, but biomass limitations restrict its widespread use. Methanol offers a solution as it can be produced from non-food sources, extending ethanol's availability. Objective: This study explores a ternary fuel blend consisting of gasoline, ethanol, and methanol as an alternative to binary gasoline-ethanol blend. The objective is to investigate if the isostoichiometric ternary blend offers equivalent fuel properties to E50 (Ethanol 50%, Gasoline 50% (v/v)) gasohol while potentially enhancing engine performance, reducing emissions, and improving combustion characteristics. Methods: A single-cylinder, four-stroke, port fuel injection spark ignition engine was used. The engine was tested with three fuels: pure gasoline, E50 blend, and an equivalent iso-stoichiometric GEM blends. Engine tests were conducted at constant load with varying engine speeds. Performance, emission, and combustion parameters were experimentally measured and compared across all fuels. Results: E50 and its equivalent blends improved brake thermal efficiency but increased brake specific fuel consumption compared to gasoline. It significantly reduced unburned hydrocarbon and carbon monoxide emissions but slightly increased nitrogen oxide emissions. Conclusion: Formulated E50 equivalent blends have identical air to fuel ratio, lower heating values as conventional binary E50 gasoline-ethanol blends. The study suggests that iso-stoichiometric GEM blends have the potential to be a viable alternative drop-in fuel for E50 in internal combustion engines. The future advancements in GEM blends, particularly in optimizing ratios, could lead to patentable inventions.

Numerical Investigations on Reducing Unburned Hydrocarbon and Carbon Monoxide Emissions in Reactivity-Controlled Compression Ignition Using Partial Reactivity Stratification with Alternative Fuels and Additive

<div>A numerical investigation has been performed in the current work on reactivity-controlled compression ignition (RCCI), a low-temperature combustion (LTC) strategy that is beneficial for achieving lower oxides of nitrogen (NO<sub>x</sub>) and soot emission. A light-duty diesel engine was modified to run in RCCI mode. Experimental data were acquired using diesel as HRF (high-reactivity fuel) and gasoline as LRF (low reactivity fuel) to check the accuracy and fidelity of predicted results. Blends of ethanol and gasoline with DTBP (di-tert-butyl peroxide) addition in a small fraction on an energy basis were used in numerical simulations to promote ignitability and reactivity enhancement of PFI charge. Achieving stable, smooth, and gradual combustion in RCCI is challenging at low loads, especially in light-duty engines, due to misfiring and poor combustion stability. DTBP is known for enhancing cetane number and accelerating combustion, and it is mixed in a PFI blend to avoid combustion deterioration. The factors governing reactivity stratification to achieve optimal combustion phasing were investigated in the present study. DTBP decomposition and its low-temperature oxidation chemistry were found to be responsible for affecting combustion phasing, heat release patterns, and emission trends. DTBP additive and different in-cylinder strategies were applied and studied to reduce unburned emissions. Adopting a multiple injection approach utilizing dual-pulse assisted in reducing HC and CO levels. It enhances combustion quality by providing adequate control over combustion phasing. Altering operating parameters like intake temperatures reduced HC, CO, and soot emissions by 97.6%, 57.6%, and 52.8%, respectively, compared to baseline gasoline/diesel RCCI data. Optimizing the injection timings of the first and second pulse helps achieve optimal combustion phasing and a 72.95% reduction in NO<sub>x</sub> emissions. The higher injection pressure of DI helped lower the CO and soot emissions by 53.33% and 51.84%, respectively.</div>

To Study the Effects of Microemulsion Based Hybrid Biofuel on Emission Characteristics of CI Engine: A Short Review

AbstractMicroemulsion based fuels (MBF) have gained significant attention in recent years due to their potential to enhance combustion efficiency, reduce emissions, and improve overall engine performance. This research paper enlightens the effects of physiochemical properties on the emission characteristics of CI engine. The microemulsions are formulated using surfactants, co‐surfactants, water or alcohols, and fuel components. The effects of density, viscosity, calorific value, cold flow properties, and cetane number along with the stability and the multi‐component characteristics of (MBF) has been taken into consideration to examine its effects on Emission characteristics such as nitrogen oxides (NOx), sulfur oxides (SOx), carbon monoxide (CO), particulate matter (PM), and unburned hydrocarbons (UHC). Microemulsion‐based fuels lower emissions of NOx and PM, recognized to the more complete combustion. The review highlights various studies that have investigated the benefits of microemulsion fuels, including reduced emissions of different pollutants and thus reduce the adverse effect on environment.In conclusion, microemulsion‐based fuels show likely physiochemical properties, as well as favorable emission characteristics, with reduced NOx, SOx, CO, PM, and UHC emissions. This study highlights the potential of microemulsion‐based fuels as environment friendly alternatives, flagging the way for further research.

Effect of ethanol content, water injection, and compression ratio on combustion and detailed emissions in an SI-GDI engine

The transportation sector accounts for 29 % of the total greenhouse gas emissions produced in the US. Steadily tightening criteria emissions and fuel efficiency requirements have led to current research efforts evaluating multiple mixed strategies or extending beyond traditional engine architectures and fuels. Ethanol is used extensively as both a fuel additive and primary fuel replacement for gasoline. Modern engines utilizing boosting or high compression ratios require fuels such as ethanol that are more resistant to pre-ignition to operate efficiently at high load conditions. Water dilution has historically been used for knock reduction and some potential has been found for emissions and efficiency improvements. The studies on these topics, however, often focus on wide-open-throttle (WOT) conditions and neglect part load where engines normally operate. This investigation evaluates the combined effects of fuel ethanol content, compression ratio, and water dilution on the combustion and emissions characteristics A 2.4L 4-cylinder naturally aspirated (NA) gasoline direct injection (GDI) engine at part load conditions.The results indicated that the varied combinations of compression ratio and fuel ethanol content did not change the typical performance or emissions results expected for either parameter alone. Water dilution only significantly degraded stability at conditions with coefficient of variation (CoV) of indicated mean effective pressure (IMEP) values near or above 3 %. Water dilution at 10 % and 20 % W/F rations reduced average oxides of nitrogen (NOx) emissions by 20 % and 40 % respectively. The water dilution effect on unburned hydrocarbons (UHCs) was more mixed with flame ionization detector (FID) results showing mixed positive and negative effects for lower ethanol content fuels and up to a 20 % increase in UHC emissions with the high ethanol fuel (E85). Fourier transform infrared (FTIR) results agreed with the fuel blend UHC sensitivity reported with the FID. Ethanol emissions were found to increase by two to three times more for each level of water dilution than unburned gasoline emissions.

Study on the performance and emissions of compression ignition engine powered by diesel and biodiesel blends

This research tested all specifications of synthesized biodiesel according to the American Society for Testing and Materials (ASTM). The spirulina micro-algae synthesized biodiesel is mixed with conventional diesel in different blends named B0, B10, B20, and B30. The number after the letter “B” indicates the ratio of (biodiesel/diesel blend), which will be used instead of net diesel for experimental purposes. Those blend specifications are investigated, and results are tabled. The variable compression ratio, single-cylinder, water-cooled, and compression ignition engine, were utilized to study the effect of algae biodiesel/diesel blends on engine performance and its exhaust emission constituents. No hardware modification was required, and the blends directly injected in the combustion chambers. The experimental investigation showed that B10 with 14.5 CR and 25 % load -as compared with net diesel- enhances almost all performance parameters more than other blends (1.7 % more brake efficiency, 12.7 % less brake specific fuel consumption, 3.45 % less in exhaust temperature, 6.7 % more in A/F ratio, and volumetric efficiency was nearly the same). It also enhances some emission parameters more than other blends (12 % less in unburned hydrocarbons (UHC′s) emissions), but with a slight increase in nitric oxides (NOX) emissions (2.4 % more than net diesel) with nearly the same values of carbon dioxide (CO2) and carbon monoxide (CO) emissions. In general, in comparison with net diesel and with icreasing blend ratio, the following results are observed: the volumetric efficiency results fluctuated with a slight difference. Both brake thermal efficiency, air/fuel ratio, and exhaust temperature were enhanced with a slight increase in brake-specific fuel consumption. For emissions: The carbon dioxide and nitrogen oxides emissions both are reduced significantly, while there was a slight increase in CO and UHC′s levels. Finally, this work recommends using the algae biodiesel as clean and substitution fuel.

Combination of high cetane diesel fuel and post injection mode in a diesel engine: A path towards lower exhaust emissions

The major objective of the presented work is to explore the effect of post injection (PI) strategy using neat diesel fuel (D100) blended with cetane number enhancer (CNE). The motive behind adding CNE in diesel fuel was to lower its self-ignition temperature and hence delay period subsequently. This can lead to more efficient combustion of post injected fuel which leads to lower incomplete combustion losses. The CNE used was Di-Tert-Butyl Peroxide (DTBP) which was blended with D100 in proportion of 1 % by volume. Initially experiments were conducted with D100 under various PI modes where variation of post injection timing (PIT) as well as post quantity (PQ) was considered. The experimental results showed that implementing PI resulted in lower smoke, unburned hydrocarbon (UHC), carbon monoxide (CO) and nitrogen oxides (NOx) emissions compared to single injection while affecting fuel consumption negatively. Then after similar experiments under various PI modes were repeated using blends of D100 and DTBP (D/DTBP) and results were compared with D100 case. It was found that addition of CNE in D100 resulted in more complete combustion of post fuel which further reduced CO and UHC emissions. The shorter delay period in case of D/DTBP blend compared to D100 case led to lower NOx emissions as well as higher smoke emissions. The obtained results revealed that PI mode with 3 mg PQ and 20° after top dead center (ATDC) PIT with D/DTBP blend offered 41.18 %, 17.55 %, 64 % and 62.5 % reduction in smoke, NOx, UHC and CO emissions respectively compared to single injection mode using D100 fuel.

An Experimental Study on the Effect of Intake Pressure on a Natural Gas-Diesel Dual-Fuel Engine

Abstract Natural gas-diesel dual-fuel (NDDF) combustion can be a viable method to reduce diesel usage in compression ignition (CI) internal combustion engines. Potential benefits of NDDF engines in comparison to conventional diesel engines include decreases in soot and carbon dioxide emissions. This study focuses on the effect of intake pressure on a dual-fuel engine with intake port injected natural gas (NG) and direct injected diesel at two engine operation conditions – low load-high speed and high load-low speed. The research work was performed on a heavy-duty, single-cylinder engine at a NG-diesel energy ratio of approximately 3:1. The results show that when the intake pressure was increased, the indicated thermal efficiency (ITE) increased for diesel combustion. The trend was similar at the high load-low speed condition but opposite at the low load-high speed condition for NDDF. ITEs of diesel combustion were generally higher than NDDF combustion due to higher unburned hydrocarbon (HC) emissions associated with the latter. For low load-high speed dual-fuel combustion, increasing intake pressure increased the HC and soot emissions, but decreased the nitrogen oxides (NOx) emissions. For high load-low speed case, increasing intake pressure caused the HC emissions to increase and the NOx and soot emissions to decrease. In-cylinder temperature measured at the tip of the diesel injector showed that the injector tip temperatures were higher for NDDF cases compared to diesel cases. These temperatures could be correlated with the combustion phasing and NOx emissions.

Study of Efficient and Clean Combustion of Diesel–Natural Gas Engine at Low Loads with Concentration and Temperature Stratified Combustion

The approach for achieving efficient and clean combustion in a diesel–natural gas (NG) heavy-duty engine at low loads was studied by computational fluid dynamics simulation. This study proposed the concentration and temperature-stratified combustion technology and clarified its mechanism. The results revealed that different stratified combustions can be organized by controlling the pressures, timings, and durations of diesel and NG injections, and stratified combustion can be classified into moderate, lean, and rich stratified combustion modes. Efficient and clean combustion can be realized simultaneously at low engine loads: the gross indicated thermal efficiency (ITEg) of engine breakthrough was improved to 47.9%, and the indicated-specific emissions of unburned hydrocarbon (ISUHC) were greatly reduced to 1.6 g/kWh, while the indicated-specific emissions of nitrogen oxide (ISNOx) remained at 0.6 g/kWh. Moreover, the detailed analysis of three typical stratified combustion modes demonstrates that coupling control of the concentration and temperature of the charge is the key to obtaining excellent engine performance. Most of the NG-stratified mixture should burn in the react ratio range of 0.4 to 0.8 for low unburned hydrocarbon emissions, low nitrogen oxides emissions, and rapid combustion. The proper temperature stratification should ensure that a high-temperature charge is around the over-lean NG mixture. This study can provide the fundamentals of stratified combustion control and feasible solutions for commercial applications of NG engines.

Retrofit of a Marine Engine to Dual-Fuel Methane–Diesel: Experimental Analysis of Performance and Exhaust Emission with Continuous and Phased Methane Injection Systems

Shipping is a highly energy-intensive sector, and fleet decarbonization initiatives can significantly reduce greenhouse gas emissions. In the short-to-medium term, internal combustion engines will continue to be used for propulsion or as electricity generators onboard ships. Natural gas is an effective solution which can be used to mitigate greenhouse gas emissions from the marine sector. Considered to be a transitional fuel, it can provide a potential reduction in CO2 emissions of around 20–30%, compared with conventional marine fuels. This work investigated the influence of diesel-injection strategies on the performance and emissions of a single-cylinder prototype compression-ignition engine for marine applications, retrofitted to run as a Low-Pressure Dual-Fuel Engine using natural gas. Two different injection systems were used: a mass flow controller enabling continuous-mode gas feeding, and a Solenoid-Operated Gas Admission Valve for marine applications, the latter allowing phased natural-gas injection. Experimental tests were focused on partial-load conditions, which are critical for dual-fuel engines, with a natural gas/diesel mass ratio of 4:1. Phased injection resulted in reductions in fuel consumption, compared to continuous mode, of up to 11%. Further experiments demonstrated reductions in fuel consumption of up to 20.7% (in equivalent diesel); on the other hand, the unburned hydrocarbon emissions which resulted were an order of magnitude larger than the reference values for full diesel, reducing the benefits in terms of greenhouse gas emissions, with a reduction in Global Warming Potential of only 3% compared to full diesel.

Performance of a Methanol-Fueled Direct-Injection Compression-Ignition Heavy-Duty Engine under Low-Temperature Combustion Conditions

Low-temperature combustion (LTC) concepts, such as homogeneous charge compression ignition (HCCI) and partially premixed combustion (PPC), aim to reduce in-cylinder temperatures in internal combustion engines, thereby lowering emissions of nitrogen oxides (NOx) and soot. These LTC concepts are particularly attractive for decarbonizing conventional diesel engines using renewable fuels such as methanol. This paper uses numerical simulations and a finite-rate chemistry model to investigate the combustion and emission processes in LTC engines operating with pure methanol. The aim is to gain a deeper understanding of the physical and chemical processes in the engine and to identify optimal engine operation in terms of efficiency and emissions. The simulations replicated the experimentally observed trends for CO, unburned hydrocarbons (UHCs), and NOx emissions, the required intake temperature to achieve consistent combustion phasing at different injection timings, and the distinctively different combustion heat release processes at various injection timings. It was found that the HCCI mode of engine operation required a higher intake temperature than PPC operation due to methanol’s low ignition temperature in fuel-richer mixtures. In the HCCI mode, the engine exhibited ultra-low NOx emissions but higher emissions of UHC and CO, along with lower combustion efficiency compared to the PPC mode. This was attributed to poor combustion efficiency in the near-wall regions and engine crevices. Low emissions and high combustion efficiency are achievable in PPC modes with a start of injection around a crank angle of 30° before the top dead center. The fundamental mechanism behind the engine performance is analyzed.

A comparative study of first and second generation biodiesel blends under quaternary injection strategies for enhanced engine performance and reduced emissions

Biodiesel is a promising renewable alternative fuel, offering compatibility with conventional engines without necessitating significant engine modifications. To facilitate the practical integration of biodiesel into engine systems, this study evaluates the performance of two different biodiesel blends (fatty acid methyl ester and hydrogenated catalytic) in a turbocharged inter-cooled diesel engine. The research employs quaternary injection techniques an advanced injection technique, which involve multiple injection events per cycle to enhance engine combustion and emission characterictics of the biodiesel blend fuels and comparing their performance and emission characteristics with those of conventional diesel. Results showed that fatty acid methyl ester biodiesel effectively reduced the CO, UHC, and NOx emissions at lower blend ratios (up to 10 %), with minimal impact on the brake-specific fuel consumption. Conversely, hydrogenated catalytic biodiesel demonstrates notable advantages in reducing fuel consumption with carbon monoxide and particle emissions, particularly for higher blend ratios (20 %), leading to improved indicated thermal efficiency. Additionally, an investigation on higher biodiesel blends under varying early injection timings showed that, optimal fuel efficiency was observed at an early injection timing of −43.6 °CA, accompanied by reductions in total particle number and unburned hydrocarbon emissions albeit with elevated carbon monoxide and nitrogen oxide emissions. These findings suggest that advanced injection strategies combined with sustainable biodiesel blends can significantly improve engine performance and reduce environmental impact, supporting the transition towards cleaner and more efficient transportation fuels.

Enhancing diesel engine performance and emission reduction through hydrogen enrichment in algal biodiesel blends.

The introduction of hydrogen into the engine could enhance its combustion efficiency and emission characteristics. The current study examines the attributes of compression ignition (CI) engines by introducing hydrogen into a biodiesel blend derived from algae. The improved thermal properties of hydrogen, when combined with algae biodiesel, significantly affect the performance, combustion, and emissions of dual-fuel engines. A study was conducted to evaluate the impact of hydrogen enrichment levels of 5%, 10%, 15%, and 20% of the nozzle volume on a biodiesel blend fuel. In comparison to diesel, algal biodiesel reduces emissions of unburned hydrocarbons (HC), carbon monoxide (CO), and oxygen (O2) by 5.19%, 3.61%, and 2.83%, respectively, while increasing nitrogen oxide (NO) emissions by 4.73%. In contrast to biodiesel, diesel demonstrated superior brake thermal efficiency (BTE) and lower specific energy consumption (SEC). Injecting hydrogen into A20 blend fuel at volumes of 5%, 10%, 15%, and 20% results in a respective increase in brake thermal efficiency of 2.65%, 2.97%, 3.50%, and 4.15%. The addition of hydrogen gas to biodiesel blends further enhances their combustion qualities, leading to elevated peak cylinder pressure, temperature, and heat release rate. The results indicate that A20H5, A20H10, A20H15, and A20H20 fuel reduced CO emissions by 3.75%, 8.75%, 12.5%, and 16.25%, respectively, compared to the A20 blend. In the same vein, HC emissions decreased by 5.76%, 10.29%, 15.52%, and 18.98%, respectively, as compared to A20 fuel. However, NO emissions rose by 5.36%, 10.20%, 15.28%, and 23.23%, respectively, for A20H5, A20H10, A20H15, and A20H20 test fuels. Ultimately, the utilization of algal biodiesel and hydrogen enrichment in diesel engines was proven to substantially reduce pollutants while increasing efficiency. This study contributes valuable insights into the intersection of renewable fuels, hydrogen enrichment, and engine technology, with the potential to drive significant advancements in sustainable transportation and environmental conservation.

Optimization of CRDI engine operating parameters using response surface methodology utilizing lemon peel oil biofuel enriched with hydroxy gas

The current study aims to optimize the operational variables of a CRDI engine in Dual-Fuel Mode (DFM). Hydroxy gas (HHO) was generated through water electrolysis using a concentric four-cylinder dry cell electrolyzer with NaOH catalyst, and it was introduced into the inlet manifold as the primary fuel. The pilot fuel consisted of Lemon Peel Oil (LPO) and pure diesel directly injected into the cylinder. An experimental matrix comprising 17 distinct runs was designed using Design of Experiments (DoE), utilizing Box-Behnken Design (BBD) based on Response Surface Methodology (RSM). The RSM model was created depending on the experimental data, and then operating parameters were optimized utilizing the desirability technique. The optimal engine operational variables were identified for the B25 LPO mixture with a constant HHO gas flow rate of 0.5 LPM, a Compression Ratio (CR) of 21.5, an Injection Pressure (IT) of 450 bars, and an inlet air temperature of 87℃. The optimized results were 30.18 % for Brake Thermal Efficiency (BTE), 9.532 g/kW-hr for Carbon Monoxide (CO) emission, 0.253 g/kW-hr for Unburned Hydrocarbon (UHC) emission, and 23.510 g/kW-hr and Nitrogen Oxides (NOx) emission, yielding a total desirability of 0.7641. Empirical validation of the optimized responses at these input conditions demonstrated their conformity to acceptable error ranges.

Phenomenological model for unburned hydrocarbon emissions from spark-ignition, pre-chamber, and dual-fuel internal combustion engines

Considering the strict regulations on the transport sector emissions, predictive models for engine emissions are essential tools to optimize high-efficient low-emission internal combustion engines (ICE) for vehicles. This aspect is of major importance, especially for developing new combustion concepts (e.g. lean, pre-chamber) or using alternative fuels. Among the gaseous emissions from spark-ignition (SI) engines, unburned hydrocarbons (uHC) are the most challenging species to model due to the complexity of the formation mechanisms. Phenomenological models are successfully used in these cases to predict emissions with a reduced computational effort. In this work, uHC phenomenological model approaches by the authors are further developed to improve the model predictivity for multiple variations including engine design, engine operating parameters, as well as different fuels and ignition methods. The model accounts for uHC contributions from piston top-land crevice, wall flame quenching, oil film fuel adsorption/desorption and features a tabulated-chemistry approach to describe uHC post-oxidation. With the support of 3D-CFD simulations, multiple novel modelling assumptions are developed and verified. The model is validated against an extensive measurement database obtained with two small-bore single-cylinder engines (SCE) fuelled with gasoline-like fuel, one with SI and one with pre-chamber, as well as against data from two different ultra-lean large-bore engines fuelled with natural gas (one equipped with a pre-chamber and one dual-fuel with a diesel pilot). The model correctly predicts the trends and absolute values of uHC emissions for all the operating conditions and the engines with an accuracy on average of 11.4%. The results demonstrate the general applicability of the model to different engine designs, the correct description of the main mechanisms contributing to fuel partial oxidation, and the potential to be extended to predict unburned fuel emissions with other fuels.

Experimental studies of thermal behavior, engine performance and emission characteristics of biodiesel / diesel / 1 pentanol blend in diesel engine

The present study investigates the significance of the utilization of biodiesel derived from waste cooking oil in diesel engines and its impact on engine output and environmental pollution after blending with diesel and 1-pentanol. The higher values of the ignition index and comprehensive performance index of 4.34 ×10−4mass/min°C2 and 13.71×10−6 mass2/min2 °C3, respectively, for D70B20P10 (70 % diesel, 20 % biodiesel & 10 % 1-pentanol by volume) indicate superior combustion performance. At full load, carbon monoxide and unburned hydrocarbon emissions from 1-pentanol blended fuels decrease significantly, ranging from 40 % to 52 % and 30.76–46.15 % compared to diesel. The D70B20P10 also showed an improved thermal efficiency of 28.68 % among all tested fuels at full load but slightly lower than diesel (29.56 %). Diesel demonstrated superior in-cylinder pressure (ICP) of 77 bar and heat release rate (HRR) of 41.1 J/ºCA owing to its excellent combustion characteristics. Introducing 5–10 % 1-pentanol in blend improved combustion, elevating ICP and HRR, attributed to enhanced fuel atomization and oxygen content. The sustainable process index value obtained for a global index per person is 0.002×10−4cap Litre-1, which lies between 0 and 1, indicates sustainability and compatibility of biodiesel production demonstration by universal biofuels (Andhra Pradesh).

Analyzing the influence of feedstock selection in pyrolysis on aviation gas turbine engines: A study on performance, combustion efficiency, and emission profiles

Commercial aviation is primarily reliant on fossil fuels, yet the depletion of these sources and the consequences of climate change necessitates the exploration of sustainable alternatives. The pyrolysis process offers a viable method for producing biofuels from various feedstocks. This research examines the combustion, emission, and performance characteristics of biofuels derived from agricultural residues, waste tyres, and plastics using pyrolysis. Pyrolysis oils derived from forestry or agricultural products exhibit high viscosity and moisture content, which impairs combustion efficiency and increases carbon monoxide (CO) from 70 % to 187 % and unburned hydrocarbon (UHC) emissions. Conversely, pyrolysis oils from plastics and waste tyres provide stable combustion with carbon monoxide and total hydrocarbon emissions (THC) comparable to those of commercial jet fuel. However, nitrogen oxide (NOX) emissions are significantly elevated from 57 % to 157 %. Engine performance tests demonstrated that forestry pyrolysis oils result in thrust loss due to their high viscosity value (14.3–113 mm2/s) and low calorific value (17.3–31.7 MJ/kg). In contrast, plastic and tyre pyrolysis oil perform similarly to commercial jet fuels but may potentially cause performance loss due to their high aromatic content (>47.67 %). Overall, upgrading the viscosity, moisture, and aromatic content of pyrolysis oils can enhance their suitability as alternative aviation fuels. These improvements could assist the aviation sector in achieving its carbon-neutral goals by making pyrolysis oils competitive with conventional jet fuels.

Design and Numerical Analysis of an Annular Combustion Chamber

Designing a combustion chamber for gas turbines is considered both a science and an art. This study presents a comprehensive methodology for designing an annular combustion chamber tailored to the operating conditions of a CFM-56 engine, a widely used high bypass ratio turbofan engine. The design process involved calculating the basic criteria and dimensions for the casing, liner, diffuser, and swirl, followed by an analysis of the cooling sections of the liner. Numerical simulations using NUMECA software and the HEXPRESS meshing tool were conducted to predict the combustion chamber’s behavior and performance, employing the κ-ε turbulence model and the Flamelet combustion model. Methane was used as the fuel, and simulations were performed for three fuel injection angles: axial, 45°, and 60°. Results demonstrate that the combustion chamber is properly dimensioned and achieves complete combustion for all configurations. The pressure ratio is 0.96, exceeding the minimum design criteria. Additionally, the emissions of unburned hydrocarbons are zero, while nitrogen oxides and carbon monoxide levels are below regulatory limits. These findings validate the proposed design methodology, ensuring efficient and environmentally compliant combustion chamber performance.

Conjoint impact of modified HHO system, compression ratio variation, and tribological enhancement of steel piston ring substrates on performance and emission characteristics of a spark-ignition engine

In these times of efforts to develop high-efficiency hydrogen-adopted or hydrogen-fueled internal combustion engines (ICEs), and concerns related to electric vehicles such as battery cost, drawbacks in harsh winter climates, low range, etc., it is important to generate original ideas in line with the manufacturing of ICEs with improved efficacy. Accordingly, this study presents a comprehensive experimental investigation to observe the cooperated effects of pulse width modulation (PWM)-controlled hydroxy (HHO) gas introduction and improvement in tribological performance of piston ring-cylinder liner mechanism on performance and emission characteristics of a spark-ignition (SI) engine (co-system). The variation of compression ratio (CR), influence of two electrolyzer types of tube electrolyzer (TE) and plate electrolyzer (PE) for production of HHO gas, and zeta potential (ZP)-based dynamic light scattering (DLS) analysis to specify the optimal catalyst concentration in de-ionized water were also observed. Electron cyclotron resonance-chemical vapor deposition (ECR-CVD) method was utilized to bombard the piston ring substrates with diamond-like carbon (DLC) atoms under high energy plasma to improve the mechanical strength of the friction surface. Using linear tribometer, the uncoated (UPR) and coated piston rings (CPR) underwent friction tests to determine the wear rate (WR), and coefficient of friction (COF) which have substantial contribution to frictional losses. The surfaces of the samples were visualized via scanning electron microscopy (SEM) and atomic force microscopy (AFM) before and after abrasion tests to analyze carbon coating and its effects on tribological performance. The observations depicted that HHO flowrate needs to be varied as the engine load and CR change, and based on these observations, PWM control unit was designed, manufactured and reprogrammed so as to adjust electrical power consumption of HHO system when needed. The aforementioned analyses ensured optimization of the overall system so as to maximize the efficiency of the test engine. The co-system with optimized parameters (CPR + HHO + PWM) yielded an increase in average brake power (Pe) up to 31%, and average reductions in specific fuel consumption (β), carbon monoxide (CO), unburned hydrocarbon (UHC), and nitrogen oxide (NOx) emissions by 17%, 25%, 19%, and 14%, respectively at engine load range from 20% to 100%. It is expected that this study will be a good guide in terms of developing high-efficient ICEs due to promising results provided by the co-system.

Combustion and emission characteristics of distilled waste plastic pyrolysis oil-gasoline blends using single cylinder motorcycle petrol engine

ABSTRACT This study assessed the performance and emissions characteristics of a single cylinder, 2-stroke motorcycle spark ignition engine (Esoo 150 cc) utilising clay-catalytically produced distilled waste plastic pyrolysis oil (DWPPO) fuel. The clay catalyst and fuel properties were analysed using established standard testing procedures. The engine performance and exhaust gas emissions were determined for various fuel blends and compared with those of commercial gasoline at various parameters. Results showed that distilled pyrolysis fuel properties (kinematic-viscosity: 6.4 × 10–7 m2/s; caloric-value: 47.82 MJ/kg) were enhanced compared to kinematic viscosity of 1.92 × 10–6 m2/s and caloric value of 44.41 MJ/kg for Crude Waste Plastic Pyrolysis Oil. Notably, chemical composition of distilled fuel collected within a temperature range of 90°C-180°C closely resembled those of pure gasoline. It was also shown that 50% Distilled Waste Plastic Pyrolysis Oil (D50WPPO) significantly improved the brake power, brake thermal efficiency and reduction in brake specific fuel consumption while operating at full load conditions with various DWPPO-Gasoline blends and pure gasoline. Unburned hydrocarbon emissions reduced by 40% when the engine was fuelled with D50WPPO. The study concluded that DWPPO can potentially be employed as a substitute of conventional gasoline without any engine modifications.